2-(Alkylthio)ethanamines in which the alkylthio group contains 8 to 12 carbon atoms are known to possess antimicrobial properties: see, for example, U.S. Pat. No. 3,291,683 and European Patent Application Publication No. 266,828. A process for the preparation of 2-(alkylthio)ethanamines from alkyl mercaptans and 2-oxazolines in the presence of a Lewis acid catalyst is taught in U.S. Pat. No. 4,086,273. In that process, for example, 2-ethyl-2-oxazoline (I) and the alkyl mercaptan (II) react in the presence of a Lewis acid catalyst to form a 2-(alkylthio)ethyl propionamide (III) which is subsequently hydrolyzed with an aqueous hydrohalic acid to the 2-(alkylthio)ethanamine hydrohalide (IV) and propionic acid. ##STR1##
The resulting solution is very acidic and is therefore corrosive to metals and human tissue. Furthermore, since the 2-(alkylthio)ethanamine hydrohalide (IV) is a quaternary amine, it is not surprising that the product behaves as a surfactant. As a result, neutralization of the reaction mixture often leads to emulsions. Formulations of such materials are often unstable with respect to phase separation, particularly when subjected to one or more freeze-thaw cycles. It would be desirable to have a stable antimicrobial formulation of 2-(alkylthio)ethanamine hydrohalides that is non-corrosive and non-settling. Moreover, it would be highly desirable to be able to form such an antimicrobial formulation directly from the reaction mixture that results from the hydrolysis of the 2-(alkylthio)ethyl propionamide (III) without any undue unit operations or waste streams.